It is known that synthetic resins, such as polyethylene, polypropylene, styrene resins, polyvinyl chloride, and polycarbonate, and organic pigments and dyes undergo deterioration, such as discoloration and reduction in mechanical strength, by the action of light so that they do not withstand long term use.
To protect these organic materials from deterioration or control the wavelengths of transmitted light, a variety of UV absorbers have hitherto been used. Known UV absorbers include benzophenone compounds, benzotriazole compounds, 2,4,6-triaryltriazine compounds, and cyanoacrylate compounds.
For example, patent literature 1 below discloses a technique of using a UV absorber, such as a benzotriazole compound or a triazine compound, in applications to optical materials. Patent literature 2 below reports a norbornene resin film containing a UV absorber.
However, the conventional UV absorber bleeds out or causes color change when added in an amount providing sufficient absorption required in optical applications.
Patent literature 3 below discloses a triazine compound, which is used in the present invention, as a UV absorber excellent in resistance to weather and heat. The compound is also reported in patent literature 4 below as a UV absorber that exhibits UV absorption suited for applications to optical films and hardly bleeds out.
Although the triazine UV absorber hardly bleeds out, exhibits UV absorption suited for applications to optical materials, and imparts resistance to thermal deterioration to synthetic resins, it has the problem of poor resistance to thermal coloration, that is, it is susceptible to coloration during, for example, high-temperature molding of synthetic resins in which it is incorporated.